Transcript 医学真菌学 （medical mycology）

医学真菌学
（medical mycology）
Comparison of fungi and bacteria
Feature
Fungi
Bacteria
diameter
4 µm
1 µm
nucleus
eukaryotic
prokaryotic
cytoplasm
with mitochondria and
endoplasmic reticulum
without mitochondria and
endoplasmic reticulum
Cell membrane
sterol present
sterol absent
Cell wall
chitin
peptidoglycan
spores
sexual and asexual
spore for proliferation
spore for survival, not for
proliferation
dimorphism
yes
No
metabolism
Require organic carbon
and no anaerobes
May do not require organic
carbon and maybe
anaerobes
Role of fungi in nature
• There are approximately 70,000
recognized species of fungi.
• Most are beneficial to humankind.
– production of food
– antibiotics and immunosuppressive drugs
– used as model systems in molecular biology
Medical Mycology
• the subject on pathogenic fungi
– Some fungi act as the plant and animal
pathogens in the agricultural industry.
– About 300 species of fungi cause human
infections.
Cellular Morphology
• A pathogenic fungi can exist either as
yeasts（酵母菌） or as mold (霉菌).
Yeasts
• Yeasts are unicellular organisms without
hyphae.
Yeast propagation
• The yeasts propagate usually by budding
and rarely by binary fission.
• If the yeast continue to propagate by
forming more and more buds, but do not
detach from one another, they will produce
elongated forms similar to hyphae called
pseudohyphae.
增殖方式
A. Yeast cells propagating by budding
B. Yeast dividing by binary fission
C. Development of pseudohyphae
Molds
• Molds have two different structural parts:
Hyphae and Spores.
• Hyphae are multi-cellular filamentous
structures.
• Hyphae form branches and the pattern of
branching is helpful for morphological
identification.
hyphae/molds
• Thus, a mold is multicellular microbes composed of
two parts: spore and hypha.
Hypha
spore
• according to hyphae do or do not have
septa they are called septate or
nonseptate hyphae.
Asexual spores
• An aerial hyphae often produces asexual
propagules named asexual spores (produced by
one cell).
• Conidium is the most common asexual spore.
Relatively large and complex conidia are
termed macroconidia, while the smaller and
simpler conidia are termed microconidia.
• When many conidia are enclosed in a sac, it is
called as endospores / sporangiospore.
Asexual spores
• Sporangiospore(孢子囊孢子):many conidia
are enclosed in a sac
Asexual spores
• Conidium （分生孢子）
– macroconidia , large and complex conidia
– microconidia the smaller and simpler conidia
macroconidia
microconidia
Asexual spores
• Thallospore (叶状孢子)
– Arthrospore (关节)
– Chlamydospore (厚膜)
– Blastospore (芽生)
Arthrospore (关节)
Chlamydospore (厚膜)
Blastospore (芽生)
Sexual spores
• Sexual spores are produced by fusion of
one male and one female cell. They
include ascospore（子囊孢子）,
basidiospore（担孢子）, oospore（卵孢子）
and zygospore（接合孢子）。
• The size, shape and location of spores are
used in laboratory to identify some species
of fungi.
Dimorphic fungi
• Some fungi exist in both yeast and mycelial forms. These
fungi are called dimorphic fungi.
Yeast form: a parasitic or pathogenic form. This form
is usually seen in tissue of patients. Can be cultured at 37
℃. Conversion to yeast form appears to be essential for
pathogenicity.
Mycelial form: a saprophytic form. This is the form
existing in nature. Can be cultured at 25 ℃.
dimorphic fungi
depending on the growth conditions
37°C
Yeast type colony
25 °C
Filamentous type colony
Culture & Colony morphology
Sabouraud culture medium.
Optimal pH 4-6.
Optimal temperature 22-28 ℃, 37 ℃ for
certain pathogenic fungi.
Aerobic.
Types of colonies
1. Yeast type colony are usually soft, opaque, 1-3
mm in size and cream colored.
2. Yeast-like type colony is similar to yeast type
colony but forms pseudohyphae.
3. Filamentous type colony have special features
such as various hyphae and special pigmentation.
• Unicellular fungi (one cell means one
fungus, e.g., yeast fungus) form yeast or
yeast-like colony.
• Multicellular fungi (many cells consist one
fungus, e.g., mold) form filamentous type
colony.
Unicellular fungi
Multicellular fungi
Multicellular fungi
Resistance
• Fungi have strong resistance to dryness, sunlight, UV light
and many chemical agents, but much sensitive to wet heat.
Drugs
• The antibiotics to treat fungal infectious diseases are quite
different compared to those to cure bacterial infectious
diseases: amphotericin B (两性霉素B), anticandine (制霉菌
素), miconazole (咪康唑), ketoconazole (酮康唑) etc.
• The most effective antifungal drugs exploit the presence
of ergosterol（麦角固醇）in fungal cell membranes that is
not found in bacterial or human cell membranes.
Fungal diseases
• Fungal diseases in human tend to be relatively benign and
few of fungal diseases are life-threatening.
• Fungal diseases are an increasing problem due to the use of
antibacterial and immunosuppressive agents. Individuals with
an altered bacterial flora or compromised defense mechanism
easily have more opportunistic fungal infections than healthy
people.
Major clinical manifestations of fungal diseases:
◇Hypersensitivity ： an allergic reaction to molds and
spores.
◇Mycotoxicosis: poisoning of human and animals by food
contaminated with mycotoxins.
◇Infectious diseases: caused by exogenous pathogenic
fungi or endogenous fungi (opportunistic infections).
◇Inducing tumors: Some mycotoxins can induce tumors
(e.g., aflatoxin causes liver cancer) (黄曲霉素).
A. Superficial mycoses:
Infections are limited to the hair or the outermost layers of skin.
common superficial mycoses（花斑癣）:
B. Cutaneous mycoses:
•
Fungi invade the keratinized layers (角化层) of skin,
hair and nails and the diseases are limited in these
layers.
•
•
The fungi causing these diseases are
termed dermatophytes (皮肤癣真菌).
The diseases are referred to as tinea (癣病).
•All tinea are caused by members of three genera:
Trichophyton (毛癣菌)
Epidermophyton (表皮癣菌)
Microsprum (小孢子癣菌)
•Unlike the superficial mycoses, cellular immune responses
may be evoked
common cutaneous mycoses:
C. Subcutaneous mycoses:
The infections involve the dermis, subcutaneous tissue, muscle
and fascia.
common subcutaneous mycoses:
D. Systemic mycoses:
the infections originate primarily from the lung and then
spread to many other organs
◇ Fungi causing systemic mycoses:
Cryptococcus neoformans (新型隐球菌)
Histoplasma capsulatum (荚膜组织胞浆菌)
Blastomyes dermatitides (皮炎芽生菌)
Paracoccidiodes brasiliensis (巴西副孢子菌)
Cryptococcus neoformans
(新型隐球菌)
• Oval, budding yeast surrounded by
characteristic thick polysaccharide capsule.
C. neoformans with capsule is negatively stained by India Ink
Disease
• Cryptococcosis（隐球菌病）
– Acute or chronic infections in the lung, bone
and skin, and meningitis
– meningitis can last several months and are
highly fatal
• No human to human transmission
– Infection follows inhalation of pigeon or
chicken droppings containing the microbe
Opportunistic mycoses
• Patients or individuals with immune
deficiency are easily suffering from
opportunistic mycoses caused by fungi
belonging to normal flora.
Opportunistic mycoses
• The major pathogens causing
opportunistic mycoses are as the following:
• Candida (假丝酵母菌)
• Aspergillus (曲霉菌)
• Mucor (毛霉菌)
• 8 species in the genus Candida can
infect humans and cause disease called
candidiasis.
• Among the 8 pathogenic species,
Candida albicans (白假丝酵母菌) is the
most common species to cause
diseases in skin, mucosa, internal
organs and central nervous system.
• Candida albicans can be found in 40-80%
of normal human beings. It is present in
mouth, intestine and vagina.
• Candida albicans is dimorphic fungus.
• Candida albicans can show germ tubes
with special shape, which used as a
diagnostic feature of the microbe.
Pseudohyphae and hyphae of Candida albicans using
Methenamine Silver Stain.
Oral thrush （ 鹅 口 疮 ） is a typical and common
disease caused by Candida albicans
Gram-staining of vaginal smear showing Candida
albicans on the epithelial cells.
第一层是自然地境界。
第二层是自发的境界。
第三层是自由的境界。
防治考试作弊的境界
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